Estimation of spatial profile of environment

ABSTRACT

Disclosed herein is a system and method for facilitating estimation of a spatial profile of an environment based on a light detection and ranging (LiDAR) based technique. In one arrangement, the present disclosure facilitates spatial profile estimation based on directing light over one dimension, such as along the vertical direction. In another arrangement, by further directing the one-dimensionally directed light in another dimension, such as along the horizontal direction, the present disclosure facilitates spatial profile estimation based on directing light in two dimensions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/467,319, filed Jun. 6, 2019, which is a national phase application ofInternational Application No. PCT/AU2017/051395, filed Dec. 15, 2017,which claims priority to Australian Patent Application No. 2016905228,filed Dec. 16, 2016, the contents of which are incorporated herein byreference in their entirety for all purposes.

FIELD OF THE INVENTION

The present invention generally relates to a system and method forfacilitating estimation of a spatial profile of an environment. Moreparticularly, the present invention relates to facilitating estimationof a spatial profile of an environment based on directing light over atleast one dimension.

BACKGROUND OF THE INVENTION

Spatial profiling refers to the mapping of an environment as viewed froma desired field of view. Each point or pixel in the field of view isassociated with a distance to form a representation of the environment.Spatial profiles may be useful in identifying objects and/or obstaclesin the environment, thereby facilitating automation of tasks.

One technique of spatial profiling involves sending light into anenvironment in a specific direction and detecting any light reflectedback from that direction, for example, by a reflecting surface in theenvironment. The reflected light carries relevant information fordetermining the distance to the reflecting surface. The combination ofthe specific direction and the distance forms a point or pixel in therepresentation of the environment. The above steps may be repeated formultiple different directions to form other points or pixels of therepresentation, thereby facilitating estimation of the spatial profileof the environment within a desired field of view.

Reference to any prior art in the specification is not, and should notbe taken as, an acknowledgment or any form of suggestion that this priorart forms part of the common general knowledge in any jurisdiction orthat this prior art could reasonably be expected to be understood,regarded as relevant and/or combined with other pieces of prior art by aperson skilled in the art.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a systemfor facilitating estimation of a spatial profile of an environment, thesystem including:

a light source configured to provide light at selected one or more ofmultiple wavelength channels, the light having at least one time-varyingattribute;

a beam director including an aperture and configured to:

spatially direct outgoing light through the aperture into theenvironment and receive at least part of the outgoing light reflected bythe environment, the outgoing light to be directed through:

a first portion of the aperture in a first direction of multipledirections into the environment along a first dimension, the firstdirection corresponding to the outgoing light at a first selectedwavelength channel; and

a second portion of the aperture in a second direction of the multipledirections into the environment along the first dimension, the seconddirection corresponding to the outgoing light at a second selectedwavelength channel, the second portion spatially overlapping with thefirst portion,

a light detector configured to detect the reflected light; and

a processing unit configured to determine at least one characteristicassociated with the at least one time-varying attribute of the reflectedlight for estimation of the spatial profile of the environmentassociated with the first direction and the second direction.

The outgoing light at the first selected wavelength channel may includea substantially identical beam shape to that of the outgoing light atthe second selected wavelength channel.

The beam director may be configured to receive the reflected light atthe first selected wavelength channel through a third portion of theaperture, and receive the reflected light at the second selectedwavelength channel through a fourth portion of the aperture, the thirdportion of the aperture spatially overlapping with the fourth portion ofthe aperture. The first, second, third and fourth portions of theaperture may be spatially overlapping with one another.

In one example, the first and second portion of the aperture maycorrespond to at least a beam waist size of 4 mm.

In one example, the third and fourth portions of the aperture correspondto at least a beam waist size of 4 mm.

The system may further comprises a light transport assembly configuredto transport the outgoing light from the light source to the beamdirector and transport the reflected light from the beam director to thelight detector, the light transport assembly including:

an outbound guided-optic route between the light source and the beamdirector for carrying the outgoing light at the first and secondselected wavelength channels; and

an inbound guided-optic route between the beam director and the lightdetector for carrying the reflected light at the first and secondselected wavelength channels.

The inbound and outbound guided-optic routes may each be selected fromthe group of: a fibre-optic route and an optical circuit route. Theoutbound guided-optic route may be associated with a smaller numericalaperture than that of the inbound guided-optic route. The outboundguided-optic route may be spatially separate from the inboundguided-optic route.

The light transport assembly may include a single-mode fibre in theoutbound guided-optic route and a multi-mode fibre in the inboundguided-optic route.

The outbound guided-optic route may spatially overlap with the inboundguided-optic route.

The light transport assembly may include a double-clad fibre in thespatially overlapped outbound and inbound guided-optic routes, thedouble-clad fibre associating with a first numerical aperture for theoutbound guided-optic route and a second numerical aperture, larger thanthe first numerical aperture, for the inbound guided-optic route.

The beam director may include one or more diffraction gratings. The oneor more diffraction gratings may comprise three diffraction gratingsarranged to turn the light in a clockwise or anti-clockwise path.

The beam director includes one or more beam compensators. At least oneof the one or more beam compensators may be located in between adjacentpairs of the one or more diffraction gratings.

The beam director may be rotatable, or may include a rotatablerefractive or reflective element, to direct light over a seconddimension substantially orthogonal to the first dimension. The lighttransport assembly may include a slip ring assembly for coupling lightwith the rotatable beam director.

The beam director includes a spectral comb filter for porting lightbetween a composite port and one of N interleaving ports, the compositeport configured to receive or provide light at any one of every N-thconsecutive wavelength channels of the multiple wavelength channels, theN interleaving ports configured to respectively provide or respectivelyreceive corresponding light at one of N groups of wavelength channels.The N interleaving ports may each be offset by a respective amount froman optical axis to provide a corresponding angular separation over asecond dimension. N may be any integer between 2 and 16 inclusive.

According to a second aspect of the invention, there is provided asystem for facilitating estimation of a spatial profile of anenvironment, the system including:

a light source configured to provide light at selected one or more ofmultiple wavelength channels, the light having at least one time-varyingattribute;

a beam director including one or more diffraction gratings andconfigured to:

spatially direct outgoing light through the one or more diffractiongratings into the environment and receive at least part of the outgoinglight reflected by the environment, the outgoing light to be directedthrough:

the one or more diffraction gratings in a first direction of multipledirections into the environment along a first dimension, the firstdirection corresponding to the outgoing light at a first selectedwavelength channel; and

the one or more diffraction gratings in a second direction of themultiple directions into the environment along the first dimension, thesecond direction corresponding to the outgoing light at a secondselected wavelength channel, any one or more of the one or morediffraction gratings being adjustably tiltable to direct light along asecond dimension substantially orthogonal to the first dimension;

a light detector configured to detect the reflected light; and

a processing unit configured to determine at least one characteristicassociated with the at least one time-varying attribute of the reflectedlight for estimation of the spatial profile of the environmentassociated with the first direction and the second direction.

Further aspects of the present invention and further embodiments of theaspects described in the preceding paragraphs will become apparent fromthe following description, given by way of example and with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C each illustrate an arrangement of a system tofacilitate estimation of the spatial profile of an environment.

FIGS. 2A and 2B each illustrate an arrangement of a light sourceproviding outgoing light having a time-varying intensity profile.

FIGS. 2C and 2D each illustrate an arrangement of a light sourceproviding outgoing light having a time-varying frequency deviation.

FIG. 3 illustrates another arrangement of a system to facilitateestimation of the spatial profile of an environment.

FIG. 4A illustrates a configuration for estimating a tiltable angle of atiltable diffraction grating in any of FIGS. 4C, 4D, 4E, 4F and 4G.

FIG. 4B illustrates an example of the relationship between zero-th orderlight intensity and the tiltable angle.

FIG. 4C illustrates another example of an angularly dispersive elementreceiving and directing light at different wavelength channels.

FIG. 4D illustrates another example of an angularly dispersive elementreceiving and directing light at different wavelength channels.

FIG. 4E illustrates another example of an angularly dispersive elementreceiving and directing light at different wavelength channels.

FIG. 4F illustrates another example of an angularly dispersive elementreceiving and directing light at different wavelength channels.

FIG. 4G illustrates another example of an angularly dispersive elementreceiving and directing light at different wavelength channels.

FIG. 4H illustrates a perspective view of an adjustably tiltablediffraction grating.

FIG. 4I illustrates a relationship between the grating tiltable angleand beam direction over the second dimension.

FIG. 4J illustrates a relationship between the grating tiltable angleand beam direction over the first dimension.

FIG. 5 illustrates the arrangement of the angularly dispersive elementillustrated in FIG. 3 receiving and directing light at a selectedwavelength channel.

FIG. 6 illustrates another arrangement of a system to facilitateestimation of the spatial profile of an environment.

FIG. 7 illustrates another arrangement of a system to facilitateestimation of the spatial profile of an environment.

FIG. 8 illustrates an example of a spectral comb filter.

FIG. 9 illustrates another arrangement of a system to facilitateestimation of the spatial profile of an environment.

DETAILED DESCRIPTION OF EMBODIMENTS

Disclosed herein is a system and method for facilitating estimation of aspatial profile of an environment based on a light detection and ranging(LiDAR) based technique. “Light” hereinafter includes electromagneticradiation having optical frequencies, including far-infrared radiation,infrared radiation, visible radiation and ultraviolet radiation. Ingeneral, LiDAR involves transmitting light into the environment andsubsequently detecting the light reflected by the environment. Bydetermining the time it takes for the light to make a round trip to andfrom, and hence the distance of, reflecting surfaces within a field ofview, an estimation of the spatial profile of the environment may beformed. In one arrangement, the present disclosure facilitates spatialprofile estimation based on directing light over one dimension, such asalong the vertical direction. In another arrangement, by furtherdirecting the one-dimensionally directed light in another dimension,such as along the horizontal direction, the present disclosurefacilitates spatial profile estimation based on directing light in twodimensions.

The inventors recognise that, in directing light over at least onedimension, the competing requirements associated with selecting anoptical beam size of the outgoing light plays a role in improvingdetection of the reflected light. In general, a larger initial beam sizecauses less beam divergence over distance. Selecting a larger initialbeam size can therefore improve the received or detected power for afixed detector area. Doing so enhances system performance, such asincreasing the signal-to-noise ratio for longer range detection and moreaccurate spatial estimation, and/or decreasing the transmitted powerrequirement for improving power consumption and conservation. However,any optical system has a certain aperture, limited for example by itsphysical footprint, which places practical limitations on the maximumbeam size. Certain solutions that direct light by angling separate lightsources transmitting light through different sub-divided portions of theaperture inevitably reduce the outgoing beam size and hence reduce thereceived power. Other solutions that involve steering light at aparticular angle by mechanically adjusting a mirror are expected torequire additional mechanical stability. In view of these competingrequirements, the inventors have devised a system and method fordirecting outgoing light in a LiDAR-based system that can substantiallymaximise utilisation of the aperture size regardless of the number ofangles or directions over which light is directed towards.

Spatial diffraction governs the optical beam divergence. For example,for a Gaussian beam (i.e. a beam having a Gaussian intensitydistribution against a radial displacement from the beam axis), the beamradius w at range z (i.e. the radial displacement at which the intensityfalls to 1/e² of the axial value) is given by w(z)=w₀√{square root over(1+(z/z_(R))²)} where w₀ is the beam waist and z_(R)=πw₀ ²/λ is theRayleigh range. For another beam profile, spatial diffraction opticscomputation may be used to determine the beam profile at range z. Unlessotherwise specified, the following disclosure is provided under theassumption that the light source provides light having a Gaussian beamprofile.

The Rayleigh range z_(R) is a useful metric to quantify the range of acollimated beam. It is the distance at which a Gaussian beam, with agiven beam waist, increases its beam size by √{square root over (2)}.The above equation for Gaussian beam is applicable to any starting pointalong the z axis, including negative z values. For a beam propagating inthe positive z direction, the beam is converging for z<0 and divergingfor z>0. The wavefront is planar at z=0 which is the beam waist andwhere the beam is neither converging nor diverging. The radius ofcurvature of the wavefront is given by R(z)=z[1+(z_(R)/z)²], where anegative radius of curvature represents a converging beam and a positiveradius of curvature represents a diverging beam.

A given range can be determined based on an appropriate beam waist sizeand radius of curvature on emission. In one arrangement, a light source(e.g. the light source 102 of FIG. 1A) emits planar wavefronts. Theoutgoing beam diverges based on the light source 102 being located atz=0 having a beam size of w(z=0). At z=z_(R), the beam size isw(z=z_(R))=√{square root over (2)}w₀. On reflection at an object, partof the outgoing light may also be scattered or diffused, in which casethe reflected light may no longer take the original Gaussian beamprofile and hence may no longer be propagating with a beam size and aradius of curvature according to Gaussian optics. In this arrangement,z_(R) may be set as the range of the system. For example, at λ=1550 nm,z_(R) is approximately 200 metres for w₀=10 mm. The corresponding rangefor such an example may be therefore set as 200 metres (i.e. from z=0 toz=z_(R)=200 metres).

In another arrangement, the light source 102 emits convergingwavefronts, such as corresponding to those at z=−z_(R). The outgoingbeam on emission converges and diverges based on the light source 102being located at z=−z_(R) having a beam size of w(z=−z_(R))=√{squareroot over (2)}w₀. The outgoing light on propagation evolves towards abeam waist w(z=0) at z=0 and a beam size of w(z=−z_(R))=√{square rootover (2)}w₀ at z=+z_(R). In this arrangement, 2z_(R) may be set as therange of the system. Compared to the first arrangement, this arrangementimproves the maximum range twice, as well as improving the spatialresolution at half the range due to the beam evolution towards a beamwaist. For example, as mentioned, at λ=1550 nm, z_(R) is approximately200 metres for w₀=10 mm. The corresponding range for such an example maybe therefore set as 400 metres (i.e. from z=−z_(R)=−200 metres toz=z_(R)=+200 metres).

Similarly, determining a beam size to accommodate a desired rangez_(object) may be based on the Rayleigh range z_(R). For example, wherethe light source 102 emits planar wavefronts (e.g. corresponding tothose at z=0), a desired range z_(object) of 100 metres may be set to beequal to z_(R), with the light source 102 located at z=0 metres, thereflecting surface at the desired range located at z=+z_(R)=100 metres.This value of z_(R) corresponds to a beam waist w₀ of roughly 7.0 mm inradius, or 14.0 mm in diameter. The beam diameter at the desired rangez_(object) of 100 m is then √{square root over (2)}w₀=9.9 mm. As anotherexample, where the light source 102 emits converging wavefronts (e.g.corresponding to those at z=−z_(R)), a desired range z_(object) of 100metres may be set to be equal to 2 z_(R), with the light source 102located at z=−z_(R)=−50 metres, the reflecting surface at the desiredrange located at z=+z_(R)=+50 metres. This value of z_(R) corresponds toa beam waist w₀ of roughly 5 mm in radius, or 10 mm in diameter, wherethis beam waist occurs at z=0 (or 50 m from the light source 102). Thebeam diameter at the desired range z_(object) of 100 m is then √{squareroot over (2)}w₀=14 mm. These examples of beam size determination aim tominimise divergence over the desired range.

The described system may be useful in monitoring relative movements orchanges in the environment. For example, in the field of autonomousvehicles (land, air, water, or space), the described system can estimatefrom the vehicle's perspective a spatial profile of the trafficconditions, including the distance of any objects, such as an obstacleor a target ahead. As the vehicle moves, the spatial profile as viewedfrom the vehicle at another location may change and may be re-estimated.As another example, in the field of docking, the described system canestimate from a container ship's perspective a spatial profile of thedock, such as the closeness of the container ship to particular parts ofthe dock, to facilitate successful docking without collision with anyparts of the dock. As yet another example, in the field of line-of-sightcommunication, such as free-space optical or microwave communication,the described system may be used for alignment purposes. Where thetransceiver has moved or is moving, it may be continuously tracked so asto align the optical or microwave beam. As further examples, theapplicable fields include, but are not limited to, industrialmeasurements and automation, site surveying, military, safety monitoringand surveillance, robotics and machine vision, printing, projectors,illumination, attacking and/or flooding and/or jamming other laser andIR vision systems.

FIG. 1A illustrates an arrangement of a spatial profiling system 100Aaccording to an embodiment of the present disclosure. The system 100Aincludes a light source 102, a beam director 103, a light detector 104and a processing unit 105. In the arrangement of FIG. 1A, light from thelight source 102 is directed by the beam director 103 in a direction inone or two dimensions into an environment 110 having a spatial profile.If the outgoing light hits an object or a reflecting surface, at leastpart of the outgoing light may be reflected (represented in solidarrows), e.g. scattered, by the object or reflecting surface back to thebeam director 103 and received at the light detector 104. The processingunit 105 is operatively coupled to the light source 102 for controllingits operations. The processing unit 105 is also operatively coupled tothe light detector 104 for determining the distance to the reflectingsurface, by determining the round-trip time for the reflected light toreturn to the beam director 103.

In one variant, the light source 102, the beam director 103, the lightdetector 104 and the processing unit 105 are substantially collocated.For instance, in an autonomous vehicle application, the collocationallows these components to be compactly packaged within the confines ofthe vehicle or in a single housing. In another variant, in a spatialprofiling system 100B as illustrated FIG. 1B, the light source 102, thelight detector 104 and the processing unit 105 are substantiallycollocated within a “central” unit 101, whereas the beam director 103 isremote from the central unit 101. In this variant, the central unit 101is optically coupled to the remote beam director 103 via one or moreoptical fibres 106. This example allows the remote beam director 103,which may include only passive components (such as passivecross-dispersive optics), to be placed in more harsh environment,because it is less susceptible to external impairments such as heat,moisture, corrosion or physical damage. In yet another variant, asillustrated in FIG. 1C, a spatial profiling system 100C may include asingle central unit 101 and multiple beam directors (such as 130A, 130Band 130C). Each of the multiple beam directors may be optically coupledto the central unit 101 via respective optical fibres (such as 106A,106B and 106C). In the example of FIG. 1C, the multiple beam directorsmay be placed at different locations and/or orientated with differentfields of view. Unless specified otherwise, the description hereinafterrefers to the collocation variant, but a skilled person would appreciatethat with minor modifications the description hereinafter is alsoapplicable to other variants.

A light wave involves an oscillating field E which can mathematically bedescribed as:

${{E(t)} \propto {\sqrt{I(t)}{\cos\left\lbrack {\varphi(t)} \right\rbrack}}} = {\sqrt{I(t)}{\cos\left\lbrack {{\frac{2\pi\; c}{\lambda_{k}}t} + {2\pi\;{f_{d}(t)}t}} \right\rbrack}}$

where I(t) represents the intensity of the light,φ(t)=(2πc/λ_(k))t+2πf_(d)(t)t represents the phase of the field, λ_(k)represents the centre wavelength of the k-th wavelength channel,f_(d)(t) represents the optical frequency deviation from the centreoptical frequency of the k-th wavelength channel, and c=299792458 m/s isthe speed of light. The light source 102 is configured to provide thelight having at least one time-varying attribute, such as a time-varyingintensity profile I(t) and/or a time-varying frequency deviationf_(d)(t). The at least one time-varying attribute imparts time-stampedinformation on the outgoing light which, on return and detection, allowsthe processing unit 105 to determine the round-trip time and hencedistance.

In one arrangement, the light source 102 is configured to provide theoutgoing light having a time-varying intensity profile I(t) at aselected one of multiple wavelength channels (each represented by itsrespective centre wavelength λ₁, λ₂, . . . λ_(N)). FIG. 2A illustratesan example of one such arrangement of the light source 102. In thisexample, the light source 102 may include a wavelength-tunable lightsource, such as a wavelength-tunable laser diode, providing light of atunable wavelength based on one or more electrical currents (e.g. theinjection current into the into one of more wavelength tuning elementsin the laser cavity) applied to the laser diode. In another example, thelight source 102 may include a broadband light source and a tunablespectral filter to provide substantially continuous-wave (CW) lightintensity at the selected wavelength.

In the example of FIG. 2A, the light source 102 may include a modulator204 for imparting a time-varying intensity profile on the outgoinglight. In one example, the modulator 204 is a semiconductor opticalamplifier (SOA) or a Mach Zehnder modulator integrated on the laserdiode. The electrical current applied to the SOA may be varied over timeto vary the amplification of the CW light produced by the laser overtime, which in turn provide outgoing light with a time-varying intensityprofile. In another example, the modulator 204 is an external modulator(such as a Mach Zehnder modulator or an external SOA modulator) to thelaser diode. In yet another example, instead of including an integratedor external modulator, the light source 102 includes a laser having again medium into which an excitation electrical current is controllablyinjected for imparting a time-varying intensity profile on the outgoinglight.

In another arrangement, as illustrated in FIG. 2B, instead of having awavelength-tunable laser 202, the light source 206 includes a broadbandlaser 208 followed by a wavelength-tunable filter 210. In yet anotherarrangement (not illustrated), the light source 206 includes multiplelaser diodes, each wavelength-tunable over a respective range and whoserespective outputs are combined to form a single output. The respectiveoutputs may be combined using a wavelength combiner, such as an opticalsplitter or an AWG.

In another arrangement, the light source 102 is configured to providethe outgoing light having a time-varying frequency deviation f_(d)(t) ata selected one of multiple wavelength channels (λ₁, λ₂, . . . λ_(N)).FIG. 2C illustrates an example of one such arrangement of the lightsource 102. The instantaneous optical frequency f and the instantaneouswavelength λ of a light field represent an equivalent physical attributeof a wave—the oscillation rate of the light field—and are related by thewave equation c=fλ. Since the speed of light c is a constant, varyingeither f or λ necessarily varies the other quantity accordingly.Similarly, as in an example illustrated FIG. 2D, varying either λ_(k) orf_(d) may be described as varying the other quantity accordingly. Inparticular, f_(d)(t) and λ_(k) are related as follows:

λ = c/(c/λ_(k) + f_(d))  and  f = c/λ_(k) + f_(d)

In practice, changes in f_(d)(t) and λ_(k) of the light source 102 maybe effected by a single control, e.g. tuning the wavelength of the lightsource 102 by, for example, an injection current into a laser diode.However, for clarity, the description hereinafter associates frequencydeviation f_(d)(t) with deviation in the optical frequency within asingle wavelength channel from its centre optical frequency, whereaschanges in λ_(k) are associated with causing the light source 102 tojump from one wavelength channel to another. For example, a smaller andsubstantially continuous wavelength change of the light source 102 isdescribed to cause a time-varying frequency deviation f_(d)(t), whereasa larger and stepped wavelength change of the light source 102 isdescribed to cause the light source 102 to jump from wavelength channelλ_(k) to λ_(k+1).

In another arrangement, the light source 102 may be configured toprovide outgoing light with both time-varying intensity profile I(t) andtime-varying frequency deviation f_(d)(t). The examples shown in FIGS.2A and 2B are both suitable for use in such an arrangement of the lightsource 102. The description above on (a) time-varying intensity profileI(t) and (b) time-varying frequency deviation f_(d)(t) applies to suchan arrangement of the light source 102.

The light source 102 is configured to provide light at selected one ormore of multiple wavelength channels. In one arrangement, the lightsource 102 provides a single selected wavelength channel at a time, suchas a wavelength-tunable laser. In this arrangement, the described system100 is capable of steering light in a particular direction based on oneselected wavelength channel at a time. In another arrangement, the lightsource 102 provides a single or multiple selected wavelength channels,such as a broadband source followed by a tunable filter, the tunablepass band of which includes the single or multiple selected wavelengthchannels. Where one selected wavelength channel is used at a time, thelight detector 104 may include an avalanche photodiode (APD) thatdetects any wavelength within the range of the multiple wavelengthchannels. Where multiple selected wavelength channels are used at atime, the light detector 104 may include a wavelength-sensitive detectorsystem, such as using multiple APDs each dedicated to a specificwavelength channels, or using a single APD for multiple wavelengthchannels, each channel being distinguishably detectable based on theirtime-varying attribute (e.g. based on a different sinusoidal modulationsuch as a modulation frequency of 21 MHz, 22 MHz and 23 MHz . . .corresponding, respectively, to 1550.01, 1550.02 and 1550.03 nm . . .channels). The description hereinafter relates to light direction byproviding a single selected wavelength channel at a time, but a skilledperson would appreciate that, with minor modifications, the descriptionis also applicable to light direction by providing multiple selectedwavelength channels at a time.

The operation of the light source 102, such as both thewavelength-tunable laser 202 (e.g. its wavelength) and the modulator 204(e.g. the modulating waveform), may be controlled by the processing unit105.

FIG. 3 illustrates an example 300 of the disclosed system in FIG. 1A. Inthis example, the system 300 includes a light transport assembly 302configured to transport the outgoing light 301 from the light source 102to the beam director 103 and transport the reflected light 303 from thebeam director 103 to the light detector 104.

The light transport assembly 302 includes optical waveguides such asoptical fibres or optical circuits (e.g. photonic integrated circuits)in the form of 2D or 3D waveguides. As described further below, theoutgoing light from the light source 102 is provided to the beamdirector 103 for directing into the environment. In some embodiments,any reflected light collected by the beam director 103 may additionallybe directed to the light detector 104. In one arrangement, for lightmixing detection, light from the light source 102 is also provided tothe light detector 104 for optical processing purposes via a directlight path (not shown) from the light source 102 to the light detector104. For example, the light from the light source 102 may first enter asampler (e.g. a 90/10 guided-optic coupler), where a majority portion(e.g. 90%) of the light is provided to the beam director 103 and theremaining sample portion (e.g. 10%) of the light is provided to thelight detector 104 via the direct path. In another example, the lightfrom the light source 102 may first enter an input port of an opticalswitch and exit from one of two output ports, where one output portdirects the light to the beam director 103 and the other output portre-directs the light to the light detector 104 at a time determined bythe processing unit 105.

The light transport assembly 302 includes a three-port element 305 forcoupling outgoing light received from a first port to a second port andcoupling received from the second port to a third port. The three-portelement may include an optical circulator or a 2×2 coupler (where afourth port is not used).

In one arrangement, the light transport assembly 302 includes anoutbound guided-optic route between the light source 102 and the beamdirector 103 for carrying the outgoing light 301 at the first and secondselected wavelength channels and an inbound guided-optic route 303between the beam director 102 and the light detector 104 for carryingthe reflected light 303 at the first and second selected wavelengthchannels (either at the same time or at different times). Theguided-optic routes may each be one of a fibre-optic route and anoptical circuit route.

In this arrangement, the beam director 103 includes beam expansionoptics 304, such as a pigtailed collimator, to expand the outgoing light301 in a wave-guided form into an expanded beam 306 in free-space formhaving a beam shape including a beam size. The solid lines and thedashed lines represent expanded beams in different selected wavelengthchannels, and are illustrated to be slightly offset for illustrativepurposes. In practice they may or may not overlap substantially orentirely in space. Subsequent figures depicting solid and dashed linesare represented in a similar manner. The beam director 103 furtherincludes an angularly dispersive element 308 providing angulardispersion of light based on the wavelength of the light. The angularlydispersive element 308 is configured to direct the expanded beam 306into at least a first direction 310A and a second direction 310B alongthe first dimension, depending on the wavelength. While the angularlydispersive element 308 is schematically illustrated in the form of atriangular element for simplicity, its actual form may differ and mayinclude multiple elements. Examples of the angularly dispersive element308 include one or more diffraction gratings, some examples of which areillustrated and further described in relation to FIGS. 4A to 4J. Thefirst direction 310A corresponds to the outgoing light at a firstselected wavelength channel λ_(A). The second direction 310B correspondsto the outgoing light at a first selected wavelength channel λ_(B).

In this arrangement, the beam director 103 includes an aperture 309,illustrated in this arrangement as a double-headed arrow on an exitsurface of the angularly dispersive element 308. Although the aperture309 is illustrated and described in this arrangement to be on the exitsurface of the angularly dispersive element 308, the aperture of thebeam director 103 may be at any point along the optical path and on anyinterface or plane (e.g. the entry surface of the angularly dispersiveelement 308) through which the beam director 103 directs light into oneor more of multiple directions. The beam director 103 is configured tospatially direct outgoing light 301 through the aperture 309 into theenvironment and receive reflected light 301 being at least part of theoutgoing light 301 reflected by the environment. The outgoing light 103directed at the two directions 310A and 310B, each associated with arespective wavelength channel, overlaps spatially within the aperture309. In particular, the outgoing light 301 at λ_(A) is directed througha first portion (marked by solid lines) of the aperture 309 in the firstdirection 310A, whereas the outgoing light 301λ_(B) is directed througha second portion (marked by dashed lines) of the aperture 309 in thesecond direction 310B. The spatial overlap between the beamsrespectively directed at directions 310A and 310B may be substantial toenable the expanded beam 306 to substantially maximise utilisation ofthe size of the aperture 309. This enablement may be contrasted with aconfiguration where two separate light sources are angled to directtheir respective light beams into different directions, so that eachdirected light beam utilises around half or less of the aperture size.The contrast is even greater in a configuration where a larger number ofseparate light sources (e.g. 10) are angled to direct their respectivelight beams into (e.g. 10) different directions, so that each directedlight beam only utilises a fraction (e.g. 1/10) of the aperture size. Incomparison, by substantially maximising utilisation of the aperture sizeof the beam director for differently directed light beams in accordancewith the present disclosure, beam divergence is desirably minimised.

In some arrangements, a similar overlap or a similar substantial overlapexists for the reflected light 303 received from these or differentdirections. That is, the reflected light 303 at λ_(A) is receivedthrough a third portion of the aperture 309 from a third directionassociated with the first direction 310A, whereas the reflected light303 at λ_(B) is received through a fourth portion of the aperture 309,spatially overlapping with the third portion, from a fourth directionassociated with the second direction 310B. In one example (such as thatillustrated in FIG. 5), the outgoing light and the reflected light donot overlap or do not substantially overlap in space at the aperture309. In an alternative example (such as that illustrated in FIG. 6), theoutgoing light and the reflected light also overlap or substantiallyoverlap in space at the aperture 309, such that the first portion, thesecond portion, the third portion and the fourth portions of theaperture 309 overlap or substantially overlap in space.

In one arrangement, the spatial overlap between the beams respectivelydirected at directions 310A and 310B is anywhere between 90 and 100% inarea. In another arrangement, the spatial overlap is anywhere between 80and 90% in area. In yet another arrangement, the spatial overlap isanywhere between 70 and 80% in area. In still yet another arrangement,the spatial overlap is anywhere between 60 and 70% in area. In still afurther arrangement, the spatial overlap is anywhere between 50 and 60%in area. A skilled person would appreciate the spatial overlap may alsobe between 0 and 50%. The level of spatial overlap may tend to be higherfor neighbouring wavelength channels or beams with a smaller angulardifference in direction, and lower for far-apart wavelength channels orbeams with a larger angular difference in direction.

The spatial overlap may be quantified based on one of a number ofmeasures. In one arrangement, the quantification is based on a widthmeasure of the overlapped beams at a certain fraction of maximum opticalintensity. For example, the width measure may be the full-width at halfmaximum (FWHM) intensity or the full-width at 1/e² maximum intensity.Alternatively, the quantification is based on a power measure of theoverlapped beams. For example, the power measure may be the fraction ofcombined optical power contained within the overlapped regions of thebeams. The selection of a particular measure to quantify the spatialoverlap depends on the beam profile. For example, overlap of Gaussianbeams, which have a single intensity peak, may be quantified moreappropriately using the FWHM measure. In another example, overlap ofhigher order beams, which have multiple intensity peaks, may bequantified more appropriately using the fractional optical powermeasure.

In one arrangement, the directions 310A and 310B may be associated withconsecutive wavelength channels of the light source 102 (i.e. thesmallest wavelength changes of the disclosed system is configured tomake as it directs outgoing light 301 by stepping through wavelengthchannels). In another arrangement, such as an arrangement involving theuse of an optical interleaver described below, the directions 310A and310B may be associated with non-consecutive wavelength channels of thelight source 102.

In some arrangements, the outgoing light 301 is adjusted to have apredetermined beam profile. The divergence of a propagating beam havingthe predetermined beam profile can be computed, and hence known, usingspatial diffraction optics. For example, for a Gaussian beam (i.e. abeam having a Gaussian intensity distribution against a radialdisplacement from the beam axis), the beam radius w at range z (i.e. theradial displacement at which the intensity falls to 1/e² of the axialvalue) is given by w(z)=w₀√{square root over (1+(z/z_(R))²)} where w₀ isthe beam waist and z_(R)=πw₀ ²/λ is the Rayleigh range. For another beamprofile, spatial diffraction optics computation may be used to determinethe beam profile at range z. Similarly computation for reversepropagation may be used to determine the outgoing beam profile for agiven desired beam profile, or a given group or range of desired beamprofiles, at the light detector 104. In some arrangement, the outgoinglight 301 at the first selected wavelength channel λ_(A) is adjusted tohave substantially identical beam shape as that of the outgoing light301 at the second selected wavelength channel λ_(B). The adjustment maybe achieved by a beam shaper optimised for use with multiple wavelengthswithin the range of the multiple wavelength channels. For example, theoutgoing beams at various wavelength channels may be adjusted to have atleast a beam waist size of 4 mm. In another example, the outgoing beamsat various wavelength channels may be adjusted to have at least a beamwaist size of 10 mm.

FIG. 4C illustrates an example of an angularly dispersive element 308Cincluding one or more multiple diffraction gratings 412. While thisexample illustrates an arrangement with three diffraction gratings, askilled person would appreciate that more or fewer diffraction gratingsmay be used. Each additional diffraction grating may provide additionaldiffraction, hence greater angular separation of the differentlydirected beams. The use of separate diffraction gratings may also allowa greater number of degrees of freedom in designing the angularlydispersive element 308C (e.g. by relaxing anti-reflection coatingrequirements by selecting angles towards normal incidence rather thangrazing incidence). However, each additional diffraction grating mayalso increase attenuation (e.g. through a finite diffraction efficiencyof the gratings). Each diffraction grating is configured to produce atleast one diffraction order (e.g. the N=1 order) that is formed byoutgoing beams directed to slightly different angles (e.g. 410A and410B) depending on the wavelength. The outgoing light directed at thetwo directions 410A and 410B, each associated with a respectivewavelength channel, overlaps spatially within an aperture 409C afterpassing the grating 412C. Similar to the angularly dispersive element308 illustrated in FIG. 3, the diffraction gratings 412 are configuredto direct the expanded beam 406 into at least a first direction 410A anda second direction 410B along the first dimension, depending on thewavelength. The first direction 410A corresponds to the outgoing lightat a first selected wavelength channel λ_(A). The second direction 410Bcorresponds to the outgoing light at a first selected wavelength channelλ_(B). FIG. 4C illustrates each diffraction grating producing onediffraction order. Each grating may produce or suppress one or moreother diffraction orders (e.g. the N=0 order and/or the N=−1 order). Asillustrated there is a substantial overlap between differently directedbeams at the aperture of each grating. In this arrangement, grating 412Areceives the expanded beam 406, and directs the beam towards grating412B, which in turn directs the beam towards grating 412C. At eachdiffraction grating, the beam is incrementally angularly dispersed. Theuse of multiple diffraction gratings increases the angular separationcompared to an arrangement with, e.g. a single diffraction grating.Further, the multiple diffraction gratings are arranged to turn thelight beam in the unidirectional beam path (e.g. clockwise asillustrated in FIG. 4C through gratings 412A, 412B and then 412C oranti-clockwise). The unidirectional beam path facilitates folding of theoptical path and reducing the size of the angularly dispersive element308 and hence the overall system footprint.

FIGS. 4D, 4E, 4F and 4G illustrate other examples of an angularlydispersive element (308D, 308E, 308F and 308G). Each of the angularlydispersive elements in these examples includes one or more multiplediffraction gratings 412 and one or more beam compensators 414. Theangularly dispersive element 308D includes three diffraction gratings412A, 412B and 412C and one beam compensator 414. The angularlydispersive element 308E also includes three diffraction gratings 412A,412B and 412C and one beam compensator 414. The angularly dispersiveelement 308F includes three diffraction gratings 412A, 412B and 412C andtwo beam compensators 414A and 414B. The angularly dispersive element308G includes two diffraction gratings 412A and 412B and two beamcompensators 414A and 414B.

The diffraction grating(s) 412 are physically separated from the beamcompensator(s) 414. The physical separation allows easier thermalexpansion management, for example by relaxing different material orcoating requirements, which may otherwise become more stringent wherethe diffraction grating(s) 412 are in intimate contact with the beamcompensator(s) 414. In some arrangements, the beam compensator(s) 414may each be in a form of a prism. The beam compensator(s) 414 areconfigured to correct for wavelength dependency on the beamcharacteristics, such as beam profile and/or beam size. In somearrangement, the beam compensator(s) 414 also provide additionaldispersion. The outgoing light directed at the two directions 410A and410B, each associated with a respective wavelength channel, overlapsspatially within a respective aperture 409D (at the exit face of thebeam compensator 414), 409E (after passing the grating 412C), 409F(after passing the grating 412C) or 409G (after passing the grating412C).

In FIG. 4D, the beam compensator 414 is not located between adjacentgratings. In contrast, in FIGS. 4E, 4F and 4G, beam compensator 414 orbeam compensators 414A and 414B are located between one or more pair ofadjacent gratings. For example, for a single-prism arrangement, theprism may be between gratings 412A and 412B (as illustrated in FIG. 4E).For a two-prism arrangement (as illustrated in FIG. 4F), one prism maybe between gratings 412A and 412B and another may be between 412B and412C. Compared to the arrangement in FIG. 4D, the arrangement in FIGS.4E-4G facilitates space-saving. The use of multiple gratings and/ormultiple beam compensators relaxes the optical requirements of thecomponents. For example, by using two (rather than one) diffractiongratings or beam compensators, the required angular dispersion perdiffraction grating or beam compensator may be reduced. The use of morediffraction gratings and/or beam compensators may also allow a greaternumber of degrees of freedom in designing the angularly dispersiveelement 408 (e.g. by relaxing anti-reflection coating requirements byselecting angles towards normal incidence rather than grazingincidence).

The angularly dispersive element (e.g. 308 and 408) is configured toreceive and direct both outgoing light 301 and reflected light 303.Although FIGS. 3 and 4 illustrate that the angularly dispersive elementis bidirectional, the outgoing and reflected light paths do notnecessarily overlap. In other words, in some arrangements, the outgoingand reflected light substantially overlap at the aperture (309 and 409),while in other arrangements the outgoing and reflected light do notoverlap at the aperture (309 and 409). FIG. 5 illustrates an example ofa partial system 500 for facilitating estimation of a spatial profile ofan environment. The partial system 500 includes the angularly dispersiveelement 308 illustrated in FIG. 3. As described above, while theangularly dispersive element 308 is schematically illustrated in theform of a triangular element for simplicity, its actual form may differand may include multiple elements, such as those angularly dispersiveelements illustrated in FIGS. 4C to 4G. In this example, the lighttransport assembly 302 includes an outbound fibre-optic route (e.g. asingle-mode fibre 302A) and an inbound fibre-optic route (e.g. amulti-mode fibre 302B). Light transported in the outbound fibre-opticroute from the light source (not shown) is expanded by expansion optics304A (e.g. a pigtailed collimator) and received by the angularlydispersive element 308. The angularly dispersive element 408 thendirects the expanded light into outgoing light in a direction based onits wavelength. For simplicity, light paths within the angularlydispersive element 308 are not shown. Further, only light paths at oneselected wavelength channel (e.g. λ_(A)) is shown. Reflected light 303,schematically illustrated as having diverged, is received by theangularly dispersive element 308 and directed back to the inboundfibre-optic route via collimating optics 304B (e.g. a pigtailedcollimator) and transported to the light detector (not shown). Takinginto account beam divergence, the numerical aperture of the inboundfibre-optic route may be larger than that of the outbound fibre-opticroute for improving light collection. Although not shown in FIG. 5, aspatial overlap exists at an aperture (not shown) of the angularlydispersive element 409 between outgoing beams 301 at differentwavelength channels directed into different directions over the firstdimension. Further, a similar spatial overlap may exist between thereflected beams 303 at different wavelength channels directed intodifferent directions over the first dimension.

In one arrangement, as illustrated in FIG. 6, parts of the outboundfibre-optic route 302A and the inbound fibre-optic route 302B may becollocated. For example, the collocated fibre-optic route may be adouble clad fibre 602, which includes a core, an inner cladding layerand an outer cladding layer. The core and inner cladding layer togetheract like a single-mode fibre having a smaller numerical aperture,whereas the inner cladding layer and the outer cladding layer togetheract like a multi-mode fibre having a larger numerical aperture. In thiscollocation arrangement 600, the double-clad fibre 602 is configured totransport light between the three-port element 305 and the expansionoptics 304 illustrated in FIG. 3. The fibre-optic route between thelight source 102 and the three-port element 305 still takes the form ofa single-mode fibre 302A for transporting outgoing light 301, whereasthe fibre-optic route between the light detector 104 and the three-portelement 305 still takes the form of a multi-mode fibre 302B fortransporting reflected light 303. Although the description on FIG. 6relates to a fibre-optic variant, a skilled person would appreciate thatwithout minor modifications the description may be applicable to otheroptical waveguide variants, such as an optical circuit variant.

The disclosure hereinbefore relates to facilitating estimation of aspatial profile by directing light over a first dimension (such as thevertical direction). The present disclosure also envisages extending todirecting light over a second dimension, substantially perpendicular tothe first dimension (such as the horizontal direction). In onearrangement, the angularly dispersive element 308 illustrated in theexample of FIG. 3, which directs light in a first dimension based on itswavelength, may include an angularly adjustable reflective element tocontrollably reflect light over a second dimension perpendicular to thefirst dimension. The angular adjustment may be controlled by an opticalpositioning system. In one example, the optical positioning system is amicroelectromechanical system (MEMS). The MEMS include an array ofindividually actuatable mirrors to reflect light. In another example,the optical positioning system is galvanometer scanning system. Comparedto some other examples, the galvanometer scanning system is relativelycompact. In yet another example, the optical positioning system is apolygonal scanning system. The polygonal scanning system includes arotatable refractive element, such as a triangular or rectangular prism,or a rotatable reflective element such as a mirror, which upon rotationabout an axis is configured to direct light over the second dimension ata scanning rate based on its rotational speed. In one form, a system forfacilitating estimation of a spatial profile may be configured to directlight into two dimensions by controlling the wavelength channel for onedimension and adjusting the angle of the angularly adjustable reflectiveelement for the other dimension. The processing unit 105 may beoperatively coupled to both the light source 102 for wavelength controland the angularly adjustable reflective element for angular control.

In another arrangement, any one or more of the diffraction gratings412A, 412B and 412C (hereinafter 412 x) in any of FIGS. 4C, 4D, 4E, 4Fand 4G may be controllably tilted about a tilting axis to direct theoutgoing light in the second dimension perpendicular to the firstdimension. The tilting axis may be substantially parallel to directionof light propagation. Where only one of the multiple diffractiongratings is controllably tilted, the diffraction grating to becontrollably tilted may be the diffraction grating which light lastpasses before being directed into the environment 110. For example, inFIG. 4C, the diffraction grating 412C may be tilted about a tilting axis414. In another example, in FIG. 4D, the diffraction grating 412C may betilted about a tilting axis 414. In yet another example, in FIG. 4E, thediffraction grating 412C may be tilted about a tilting axis 414. Instill yet another example, in FIG. 4F, the diffraction grating 412C maybe tilted about a tilting axis 414. In still yet another example, inFIG. 4G, the diffraction grating 412B may be tilted about a tilting axis414. A skilled person would appreciate that the tilting axis 414 may notnecessarily pass through the centre of the diffraction grating 412 x.For example, the tilting axis 414 may be offset from the centre of thediffraction grating 412 x. Further, the tilting axis 414 may notnecessarily pass through the diffraction grating 412 x.

As illustrated in FIG. 4H, the diffraction grating 412 x is adjustablytiltable about the tilting axis 414, parallel to a direction of an inputbeam and/or perpendicular to the plane defined by the lines of thediffraction grating 412 x. An adjustment of the tiltable angle 416 ofthe diffraction grating 412 x causes a corresponding change in theoutput beam's direction 418 along the second dimension. The sensitivity(e.g. based on a comparison between a range of tiltable angles 416 ofthe diffraction grating 412 x compared to a range of the directions 418of the output beam) may range between approximately 0.5 to 2 degrees ofoutput beam direction over the second dimension per degree of gratingtilt. In one instance, beam direction over 80 degrees can be achieved bytilting a single diffraction grating by 40 degrees (i.e. a sensitivityof 2.0 degrees). In another instance, beam direction over 120 degreescan be achieved by tilting a single diffraction grating by 180 degrees(i.e. a sensitivity of 0.67 degrees).

While a change in the grating tilt angle predominantly results in beamdirection in the second dimension, it may also manifest in a, usuallycomparatively smaller, change in the beam direction over the firstdimension (i.e. the wavelength dependent dimension). This manifestationmay in one arrangement advantageously extend the range of the beamdirection along the first dimension. For example, as illustrated inFIGS. 4I and 4J, an adjustment of the tiltable angle of the diffractiongrating 412 x over 140 degrees causes the output beam to be directedover 120 degrees along the second dimension (FIG. 4I), but over 5degrees along the first dimension (FIG. 4J) out of 30 degrees total beamdirection over the first dimension.

In one arrangement, the beam director 103 is configured to estimate thetiltable angle 416 based on the non-diffracted optical intensity throughthe tiltable diffraction grating 412 x. Tilting the tiltable angle 416about the tilting axis 414 of the tiltable diffraction grating 412 xaffects the efficiency of light diffraction towards the non-zero-thdiffraction order(s) 430. The changes in this efficiency manifest in avariation in light intensity through the zero-th order 440 of thediffraction grating 412 x. As illustrated in FIG. 4A, a photodetector450 may be positioned in the path of the light 420 directed towards andbeyond the diffraction grating 412 x. The photodetector 450 measuresintensity of light through a tiltable diffraction grating 412 x alongits zero-th order 440, based on which the tiltable angle 416 may beinferred. FIG. 4B illustrates an example of a relationship of a measureof the zero-th order optical intensity versus tiltable angle 416 of thetiltable diffraction grating 412 x. The zero-th order optical intensitygenerally varies periodically, in a sinusoidal-like fashion, as thetiltable diffraction grating 412 x is rotated about the axis 414. Forexample, successive local minima represent lowest optical intensitiesmeasured along the zero-th order. These local minima are separated by180 degrees of rotation of the tiltable diffraction grating 412 x. UsingFIG. 4B as calibration, the tiltable angle 416 may be estimated based ona measurement of the zero-th order optical intensity.

FIG. 7 shows partially another arrangement 700 of a system forfacilitating estimation of a spatial profile by directing light over twodimensions. The system 700 includes a beam director 103 which in turnsincluding the angularly dispersive element 308 or 408, respectivelyillustrated in FIGS. 3 and 4, which directs light in a first dimension(e.g. the vertical direction) based on its wavelength. In the system700, the angularly dispersive element 308 or 408 is be mounted orotherwise supported on a rotatable support 702. The rotatable support702 is rotatable over a second dimension (e.g. the horizontal direction)substantially perpendicular to the first dimension. The system 700 mayinclude a slip ring 704 to mechanically and/or optically couple betweenthe light transport assembly 302 and the light detector 104. In oneform, a system for facilitating estimation of a spatial profile may beconfigured to direct light into two dimensions by controlling thewavelength channel for one dimension and adjusting the angle or rotationof the rotatable support 702 for the other dimension. The processingunit 105 may be operatively coupled to both the light source 102 forwavelength control and the rotatable support 702 for angular orrotational control. In an alternative arrangement (not illustrated), thebeam director 103 may rotate about an internal axis, rather thanrevolving around a rotational axis of a rotatable support. For example,the beam director 103 may rotate about the beam expansion optics 304,such as a pigtailed collimator, along a rotational axis that aligns withthe direction of the expanded beam 306 in FIG. 3 or the expanded beam406 in FIGS. 4A-4G.

In another arrangement, a system for facilitating estimation of aspatial profile by directing light over two dimensions includes anoptical interleaver having output ports (interleaving ports) spatiallyoffset from an optical axis (e.g. of expansion optics) to provide lightdirection over a second dimension. FIG. 8 illustrates a spectral combfilter in the form of an optical interleaver 800 for porting lightbetween an input (composite) port and one of N output ports(interleaving ports), where N=2^(x) where x is a positive integer. InFIG. 8, N is 8. In another arrangement, N may be 2 or 16. The opticalinterleaver 800 includes multiple interferometric segments (e.g. 802)each including splitters 804 at the respective ends of the segmentseparated by two interferometric paths having an optical path difference806. Each segment 802 in a branch is divided into two segments in thenext branch. The optical path difference doubles from one branch to thenext (e.g. ΔL, 2ΔL, 4ΔL . . . etc). The composite port 806 is configuredto receive or provide light at any one of every N-th consecutivewavelength channels (e.g. λ₁, λ_(N+1), λ_(2N+1) . . . ) of the multiplewavelength channels. The N interleaving ports 808 are configured torespectively provide or respectively receive corresponding light at oneof N groups of wavelength channels. FIG. 9 illustrates a system 900including the optical interleaver 800, N beam directors 103 andexpansion optics 902. The beam director 103 receives light fromrespective interleaving ports that are spatially offset over a seconddirection from an optical axis of the expansion optics 902. The beamdirectors 103 each direct the light over a first dimension (e.g. intoand out of the page), whereas the expansion optics 902 angles thedirected light from the beam directors 103 to be further directed over asecond dimension (e.g. up and down the page). A skilled person wouldappreciate that, instead of or in addition to using the opticalinterleaver, other forms of a spectral comb filter, such as aFabry-Perot resonators or a Mach-Zehnder interferometer, may be used.

In another arrangement, instead of using an optical interleaver 800, oneor array of reflective elements, such as microelectromechanical systemsor MEMS, may be used to provide light direction over a second dimension.The one or array of reflective elements may be configured to directlight towards the expansion optics 902 for collimation and expansion.This arrangement facilitates adjustment over continuous angles, ratherthan discrete angles as in the case for the optical interleaver 800, inthe second dimension.

Now that arrangements of the present disclosure are described, it shouldbe apparent to the skilled person in the art that at least one of thedescribed arrangements have the following advantages:

-   -   The utilisation of the aperture size of the beam director is        maximised regardless of the range or number of angles over which        light is directed.    -   The one dimensional beam director may be added to a variety of        different mechanical or optical systems to provide bean        direction in a second direction.

It will be understood that the invention disclosed and defined in thisspecification extends to all alternative combinations of two or more ofthe individual features mentioned or evident from the text or drawings.All of these different combinations constitute various alternativeaspects of the invention.

The invention claimed is:
 1. A system for facilitating estimation of aspatial profile of an environment, the system including: a light sourceconfigured to provide light at selected one or more of multiplewavelength channels, the light having at least one time-varyingattribute; a beam director including an aperture and configured to:spatially direct outgoing light through the aperture into theenvironment and receive at least part of the outgoing light reflected bythe environment, the outgoing light to be directed through: a firstportion of the aperture in a first direction of multiple directions intothe environment along a first dimension, the first directioncorresponding to the outgoing light at a first selected wavelengthchannel; and a second portion of the aperture in a second direction ofthe multiple directions into the environment along the first dimension,the second direction corresponding to the outgoing light at a secondselected wavelength channel, the second portion spatially overlappingwith the first portion; a light detector configured to detect thereflected light; and a processing unit configured to determine at leastone characteristic associated with the at least one time-varyingattribute of the reflected light for estimation of the spatial profileof the environment associated with the first direction and the seconddirection.
 2. The system of claim 1 wherein the outgoing light at thefirst selected wavelength channel includes a substantially identicalbeam shape to that of the outgoing light at the second selectedwavelength channel.
 3. The system of claim 1 wherein the beam directoris configured to receive the reflected light at the first selectedwavelength channel through a third portion of the aperture, and receivethe reflected light at the second selected wavelength channel through afourth portion of the aperture, the third portion of the aperturespatially overlapping with the fourth portion of the aperture.
 4. Thesystem of claim 3 wherein the first, second, third and fourth portionsof the aperture are spatially overlapping with one another.
 5. Thesystem of claim 1 wherein the first and second portion of the aperturecorrespond to at least a beam waist size of 4 mm.
 6. The system of claim4 wherein the third and fourth portions of the aperture correspond to atleast a beam waist size of 4 mm.
 7. The system of claim 1 furthercomprising a light transport assembly configured to transport theoutgoing light from the light source to the beam director and transportthe reflected light from the beam director to the light detector, thelight transport assembly including: an outbound guided-optic routebetween the light source and the beam director for carrying the outgoinglight at the first and second selected wavelength channels; and aninbound guided-optic route between the beam director and the lightdetector for carrying the reflected light at the first and secondselected wavelength channels.
 8. The system of claim 7 wherein theinbound and outbound guided-optic routes are each selected from thegroup of: a fibre-optic route and an optical circuit route.
 9. Thesystem of claim 7 wherein the outbound guided-optic route is associatedwith a smaller numerical aperture than that of the inbound guided-opticroute.
 10. The system of claim 7 wherein the outbound guided-optic routeis spatially separate from the inbound guided-optic route.
 11. Thesystem of claim 10 wherein the light transport assembly includes asingle-mode fibre in the outbound guided-optic route and a multi-modefibre in the inbound guided-optic route.
 12. The system of claim 7wherein the outbound guided-optic route spatially overlaps with theinbound guided-optic route.
 13. The system of claim 12 wherein the lighttransport assembly includes a double-clad fibre in the spatiallyoverlapped outbound and inbound guided-optic routes, the double-cladfibre associating with a first numerical aperture for the outboundguided-optic route and a second numerical aperture, larger than thefirst numerical aperture, for the inbound guided-optic route.
 14. Thesystem of claim 1 wherein the beam director includes one or morediffraction gratings.
 15. The system of claim 14 wherein the one or morediffraction gratings comprise three diffraction gratings arranged toturn the light in a clockwise or anti-clockwise path.
 16. The system ofclaim 14 wherein any one or more of the one or more diffraction gratingsare adjustably tiltable to direct light along a second dimensionsubstantially orthogonal to the first dimension.
 17. The system of claim16 wherein the beam director includes one or more beam compensators. 18.The system of claim 17 wherein at least one of the one or more beamcompensators are located in between adjacent pairs of the one or morediffraction gratings.
 19. The system of claim 1 wherein the beamdirector is rotatable, or includes a rotatable refractive or reflectiveelement, to direct light over a second dimension substantiallyorthogonal to the first dimension.
 20. The system of claim 1, whereinthe beam director includes a spectral comb filter for porting lightbetween a composite port and one of N interleaving ports, the compositeport configured to receive or provide light at any one of every N-thconsecutive wavelength channels of the multiple wavelength channels, theN interleaving ports configured to respectively provide or respectivelyreceive corresponding light at one of N groups of wavelength channels.21. The system of claim 20 wherein the N interleaving ports are eachoffset by a respective amount from an optical axis to provide acorresponding angular separation over a second dimension.
 22. The systemof claim 21 wherein N is any integer between 2 and 16 inclusive.